The error message is telling exactly what the problem is. You are missing a "using" statement and/or missing an assembly reference in your project. You need to add the assembly or namespace where "crpPlayer" is defined.

What kind of namespace. I'm sorry I couldn't identify because I'm following a video. And then that error pop out but in the video there are no errors. Can you tell me what kind of namespace? I'm sorry I'm still a novice in ASP.net.